An analog to digital converter device includes a capacitor array, a digital logic circuit, and a comparator circuit. The capacitor array includes first capacitors, a capacitor to be calibrated, and compensation capacitors. The digital logic circuit performs a calibration on the capacitor to be calibrated, in order to calibrate a weighed value of the capacitor to be calibrated according to a decision signal, and converts an input signal to bits via the capacitor array after the calibration is performed. The comparator circuit compares a testing signal with a predetermined voltage to generate the decision signal. The testing signal is generated by the first capacitors and the capacitor to be calibrated in response to the calibration. The digital logic circuit further selects at least one of the compensation capacitors, in order to adjust a digital code corresponding to a calibrated weighed value to be an integer expressed by the bits.